DISCUSSION

Our study has demonstrated that 5-meter gait speed can be feasibly measured at the time of ED discharge to identify frail older adults at risk for functional decline and return to the ED. Two of five older adults leaving the ED were found to be slow walkers, which, compounded on their greater burden of comorbidity and functional disability, increased by threefold their risk of short-term further functional decline. Functional decline was a harbinger for future ED usage over the ensuing 6 months. Gait speed was not predictive of short-term repeat ED visits within the first month after ED discharge. Finally, grip strength was not predictive of functional decline or repeat ED visits; therefore, gait speed should be favored as a screening test for frailty in this setting.

To date, most of the evidence on frailty in the ED has been based on rapid geriatric case finding questionnaires (Identification of Seniors At Risk [ISAR], Triage Risk Screening Tool [TRST], PRISMA-7, Silver Code) and global assessments of accumulated deficits (Frailty Index [FI], Clinical Frailty Scale [CFS], Brief Geriatric Assessment [BGA]).^{Reference Theou, Campbell, Malone and Rockwood6,Reference Preston, Chambers, Campbell, Cantrell, Turner and Goyder7,Reference Launay, de Decker, Kabeshova, Annweiler and Beauchet16,Reference Beauchet, Fung and Launay17} The case finding questionnaires are practical for front-line screening at the time of ED triage,^{Reference Bullard, Melady and Emond18} but their specificity to predict adverse outcomes is modest. The FI and CFS are validated predictors of hospital admission, length of stay, death, and functional decline,^{Reference Hastings, Purser, Johnson, Sloane and Whitson19–Reference Brousseau, Dent and Hubbard23} but their practical utility is contingent on being able to collect the required data elements in real-time.^{Reference Searle, Mitnitski, Gahbauer, Gill and Rockwood24} The busy ED clinician can “ballpark” a CFS rating, but this type of rating is poorly reproducible^{Reference Bouillon, Kivimäki and Hamer25} and no better than subjective judgment.^{Reference Sirois, Griffith and Perry26}

Phenotypic assessments of frailty, particularly those based on physical tests, are objective and generalizable across clinicians and institutions.^{Reference Afilalo9} This is pertinent in the ED where clinicians have limited time for questionnaires, acutely ill patients may have limited ability for recall, and over time, a given patient may visit multiple different EDs and be seen by a variety of clinicians. However, acutely ill patients may have limited ability to complete physical tests and the resulting scores may not be indicative of their true capabilities. Fallon et al. cited this concern to justify why their prospective cohort study failed to observe an association between frailty and mortality in ED patients, with frailty having been measured by a questionnaire and grip strength test.^{Reference Fallon, Kilbane and Briggs27} Tucker et al. sought to pilot test the feasibility of the gait speed test by ED nurses, and although the nurses agreed that “gait speed screening should be implemented in the ED as a standard of care for older patients,” they managed to collect these data in only 21/35 patients.^{Reference Tucker, Evans, Clevenger, Ardisson and Hwang28}

Sirois et al. attempted to circumvent the ED patients’ acute physical limitations by asking them to self-rate their lower-extremity strength, energy, and weight loss,^{Reference Sirois, Griffith and Perry26} finding this to be predictive of functional decline 3–6 months after an ED visit for a minor injury. Martin-Sanchez et al. similarly asked patients to self-rate their gait speed, upper-extremity strength, activity, energy, and weight loss, finding this to be predictive of 30-day mortality after an ED visit for decompensated heart failure.^{Reference Martín-Sánchez, Rodríguez-Adrada and Mueller29} Despite these two promising studies, Stiffler et al. reported the accuracy of self-rated gait speed and grip strength to be weak in ED patients and concluded that objective measurements should be favored.^{Reference Stiffler, Finley, Midha and Wilber30} A systematic review by Eagles et al. did not identify any high-quality studies using gait speed as a quantitative assessment in the ED; moreover, nonquantitative assessments of mobility (mainly the “Get Up & Go” test) were not predictive of hospital admissions or ED visits.^{Reference Eagles, Yadav, Perry, Sirois and Emond31} Thus, the current study was designed to objectively measure gait speed in the ED and demonstrate its feasibility and prognostic value.

Several limitations merit discussion. First, this was a single-center study that should be confirmed by a larger multi-center study before recommending gait speed for widespread use. It should be noted that gait speed has been validated in acute care settings outside of the ED, including medical wards and cardiovascular units.^{Reference Peel, Kuys and Klein32} While gait speed has been shown to outperform more elaborate frailty scales to predict adverse outcomes,^{Reference Purser, Kuchibhatla, Fillenbaum, Harding, Peterson and Alexander33,Reference Afilalo, Mottillo and Eisenberg34} it remains a screening test, and broader assessments are required to capture the multiple facets of frailty. Second, this study used research assistants to measure gait speed during working hours and did not test the implementation by clinical staff during all hours. Although this may affect the generalizability of our results, it is unlikely to have introduced a selection bias because enrolled and nonenrolled patients were generally similar and the reasons for not approaching patients were often logistical in nature. Third, ED visits were ascertained by reviewing medical records at the study center and interviewing patients by phone, such that a minority of ED visits occurring at other centers and not recalled by patients may have been missed leading to a nondifferential information bias. Fourth, the number of covariates analyzed in relation to the number of events for repeat ED visits (mainly at 1 month) may have led to residual confounding or overfitting.^{Reference Vittinghoff and McCulloch35} Lastly, the downstream effect of testing for frailty was not assessed and will require dedicated intervention studies. A systematic review identified 18 intervention studies focused on comprehensive geriatric assessment and delivery of care during the ED stay, although few studies addressed the optimization of care after the ED discharge.^{Reference Preston, Chambers, Campbell, Cantrell, Turner and Goyder7}